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Abstract: The Hsinchu Science-based Industrial Park (HSIP) is the hi-tech manufacturing hub of Taiwan. Wastewater from the HSIP contains numerous nano-sized silicate particles whose size distributions peak at 2 and 90nm. A 3–5mgl−1 as Al dose of polyaluminum chloride (PACl) was used in the field to coagulate these particles, but the removal efficiency was low. Laboratory scale tests indicated that although PACl coagulation removed 52% of the turbidity and 48% of the chemical oxygen demand (COD) from water, its effect on nano-particle removal was minimal. About 58% of the soluble COD was associated with colloidal Si particles. A light scattering test and transmission electron microscopy (TEM) demonstrated that the nano-particles agglomerated in approximately linear aggregates of sizes 100–300nm. Prolonged contact between residual PACl and the nano-particles generated large aggregates with sizes of up to 10μm and a fractal dimension of 2.24–2.63. The results presented herein should be of interest in the processing of “high-tech” wastewater that contains nanosized silica particles. [Copyright &y& Elsevier]

As is often assumed, rapid mix effectively distributes the dosed coagulant in suspension to promote subsequent flocculation of suspended particles and coagulant molecules. This study determined that the role of rapid mix is considerably more complex than conventionally assumed. Particles in the raw water samples from the Banxing Water Works of Taipei City were coagulated at high shear environment, during which flocs of size 40–70 μm were produced. The produced floc interior was compacted, and residual turbidity and the amount of dissolved natural organic matter (NOM) in suspension were substantially reduced. The subsequent stage of rapid mix slightly reduces floc size, further compacts the floc interior, and expels fine particles and some adsorbed NOM from the flocs. A sudden reduction in shearing rate produced large sized flocs with not so compact structures. Moreover, this action released fine particles from flocs into the suspension and enhanced adsorption of NOM onto solid surfaces. [ABSTRACT FROM AUTHOR]

The Hsinchu Science‐based Industrial Park (HSIP) is a “high‐tech” manufacturing base in Taiwan. Wastewater from the HSIP contains numerous nanoparticles, which are difficult to remove by conventional coagulation‐sedimentation processes, and are the main foulants to ultrafiltration (UF) and reverse‐osmosis (RO), membrane in filtration. This investigation observed that the coagulation rates of nanoparticles in wastewater could be significantly increased by raising the solution temperature to over 65°C, thus yielding large and compact aggregates. The proposed thermal treatment could considerably reduce the fouling potentials of UF and RO membranes, and thus represents a suitable pre‐treatment for producing clean water from HSIP wastewater. [ABSTRACT FROM AUTHOR]